[ntp:questions] Re: is there a way to "lock" the drift frequency

Hal Murray hmurray at suespammers.org
Thu Nov 20 01:35:31 UTC 2003

>Timer interrupts have no buffering to fall back on.  A UART generates
>an interrupt when there are still several characters free in the
>buffer, so a lag of 10-20ms is no big deal.  Most other I/O devices
>are similarly buffered.

Lost timer interrupts mean that some chunk of code has disabled interrupts
for 10 ms.  The people I hang out with would call that broken.  (and fix
it if they could)  It's probably possible to build a system where that makes
sense, but it generally breaks various things, like time keeping and other
IO gear.

As for buffering on RS232 links...  It depends upon what speed you are
running at.  115K bits/second is common for talking to development
systems.  That's 11K bytes per second or 115 bytes in 10 ms.  Most
FIFOs are not that big.

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